add gettext to build release script

new dependency for this build means we need it

Author: niftynei

contrib/Dockerfile.builder

@@ -35,6 +35,7 @@ RUN apt-get -qq update && \
 	shellcheck \
 	libxml2-utils \
 	wget \
+	gettext \
 	xsltproc \
 	zlib1g-dev && \
 	rm -rf /var/lib/apt/lists/*

contrib/Dockerfile.builder.i386

@@ -23,6 +23,7 @@ RUN apt-get -qq update && \
 	libprotobuf-c-dev \
 	libsqlite3-dev \
 	libgmp-dev \
+	gettext \
 	git \
 	python \
 	python3 \